Cancer is a major and often fatal disease. Accordingly, the development of new therapies for cancer is an ongoing process of outmost importance. The majority of cancers are present as solid tumours, such as lung cancer, breast cancer and prostate cancer, while others represent haematological and lymphoid malignancies, such as leukaemias and lymphomas.
During the recent decade much interest has been devoted to drugs directed to specific target molecules. Molecules regulating cell proliferation and death, such as Tyrosine Kinase Receptors (RTKs) for growth factors, are among targets for this type of therapeutic approach. Two classes of compounds targeting RTKs are currently used in clinical practice: monoclonal antibodies and tyrosine kinase inhibitors. The first approved targeted therapies were trastuzumab, a monoclonal antibody against HER2, for treatment of metastatic breast cancer, and imatinib, a small tyrosine kinase inhibitor targeting BCR-Abl, in Chronic Myeloid Leukemia. Despite good treatment results many of the treated patients have developed drug resistance, often due to the activation of alternative RTKs pathways. Currently there is a general idea that molecules interfering simultaneously with multiple RTKs might be more effective than single target agents. There are a few recently approved drugs, such as sorafenib and sunitinib, that apparently target multiple pathways and could serve as representatives of this new generation of anti-cancer drugs (e.g. Gossage and Eisen, Targeting multiple kinase pathways: a change in paradigm. Clin Cancer Res (2010) vol. 16(7) pp. 1973-8).
Another example of an important target for cancer chemotherapy is tubulin. The targeting drugs in this therapy interrupt microtubule spindle-mediated chromosome segregation, arrest the dividing tumor cells in mitosis and subsequently induce apoptosis. Existing drugs are targeting microtubules via two main mechanisms, e.g. molecules of the taxane class (that stabilize the tubulins) and several vinca alkaloids (destabilizers). The potency, efficacy, and widespread clinical use of these agents of natural origin in a variety of cancers, e.g. breast, ovarian, prostate, lung, leukaemias, and lymphomas, stand testament to the importance of tubulin and its role in cancer growth. Derivatives and analogs of these plant compounds are constantly being isolated or synthesized to find more efficacious anticancer agents. For examples of novel tubulin polymerization inhibitors, see e.g. WO 2009/070645 and US 2010/0279410.
In the clinic cancer chemotherapy is used in attempts to cure or palliate the disease. In most cases this therapy is delivered in the form of combination chemotherapy, i.e. when two or more drugs having different modes of action are used together in order to optimise the effect on the cancer cells and to minimise side effects. The results obtained with chemotherapy vary according to tumour type. Some tumours are very sensitive and the treatment has a high probability of leading to beneficial treatment results including cure of the disease. Examples of this type of tumours are acute leukaemias, malignant lymphomas, testicular cancer, chorion carcinomas, and Wilms tumour. Other types of cancer chemotherapy can result in effective palliation and prolonged survival. Examples of such tumours are breast cancer, colorectal cancer, ovarian cancer, small-cell lung cancer, bladder cancer, multiple myeloma, and chronic leukaemias of both the lymphatic and myeloid type. Primary drug resistant tumours which respond poorly to classical chemotherapy include malignant glioma, melanoma, prostate cancer, sarcomas, and gastrointestinal tumours other than colorectal cancers (see e.g. DeVita, Hellman, and Rosenberg: Cancer: Principles & Practice of Oncology, Eighth Edition 978-0-7817-7207-5).
Certain pyrimidine compounds and their potential use in the treatment of cancer are disclosed in for example WO2003/030909, WO2003/063794, WO2004/056807, WO2004/056786, US2004/220177, WO2005/013996, WO2006/133426, WO2007/085833, WO2008/128231 and WO2009/063240.
What is needed in the art are targeted drugs that work in a specific manner, being selective in eliminating subpopulations of cells involved in tumour survival and progression. The present invention provides novel pyrimidine compounds having a surprisingly efficient and selective antiproliferative activity. Hence, these novel compounds are useful in the treatment of proliferative diseases, such as cancer.